Timber Frame Options for External Noise

[Tim_C]

My site is about 50m from a railway line, so external noise is a consideration when deciding on timber frame spec. For all options the aim is for high airtightness, triple glazing and assumes fibre cement external cladding (or similar)

 

As I see it we have these options:

1. 140mm studs (PIR between)plus 25/50mm internal PIR. Cheapest but I assume worst for sound transfer.
2. Same as option 1 but additional sound boarding internally (e.g double plasterboard, acoustic plasterboard).
3. 300mm twin stud filled cellulose. I understand this is best, but more expensive with thicker wall buildup.
4. Other options I haven't thought of?

 

So I have a dilemea, with a trade off between cost/sound insulation and wall thickness. I'm trying to understand if the premium options are worth the additional price. What are people's experience of these options in the real world? Or any other options worth considering?

[-rick-]

Rockwool (or similar heavy mineral wool) installed instead of PIR. Rockwool is less insulating that PIR so would need thicker walls if you want the same level of insulation. You are already looking at high levels of insulation (beyond legal minimums - which themselves are a lot stricter than they used to be) so maybe the reduced insulation doesn't matter if you kept the wall thickness the same*. If it does a compromise is to do rockwool between the studs but keep the PIR internally. Not as good sound insulation but better thermally.

 

My other thought is to consider what you are doing between the house and the rail line. Trees? Hedges? Fences? Even a rain screen that is somewhat isolated from the main building structure may help stop noise getting to the walls in the first place. Having said that ignoring the railway I would personally avoid option 1 anyway. The decrement delay and sound insulation properties of mineral wool/cellulose/similar are a great advantage for any property.

 

* Beyond a certain point you might gain more from investing in better airtightness/good MHVR than having thicker insulation.

 

 

[-rick-]

Based only on watching grand designs in the past (memory is vague). I seem to recall a lot of 'noise' can be transmitted through the soil as a lower rumble. IIRC there are some mitigations you can do about this so that may be worth researching too.

 

Depends a fair bit on what sort of railway is nearby. Fast passenger trains, slow commuter trains, freight?

[Bramco]

You also need to take the roof into account.  Especially if you are planning vaulted ceilings.